1. Field of the Invention
The present invention relates to devices for filtering and purifying water to make such water potable, and more particularly to a portable water filtering and purifying device that can be used to quickly and simply destroy, neutralize or remove very small contaminants and other disease causing elements from such water.
2. Description of Related Art
Contaminated drinking water is one of the world's leading causes of health problems. While poor quality drinking water is encountered on a daily basis by millions throughout the world, and is particularly prevalent in less developed countries, ensuring the safety of a supply of water is also very problematic in developed countries, as well as for soldiers, hikers, international travelers and others. Certain well known waterborne diseases are common in untreated water, caused by microbial agents including protozoan parasites that cause Giardiasis and Cyclosporasis, and Crytosporidium parvum, viruses such as the hepatitis A and other viruses, and bacterium such as E. coli, salmonella typhi which causes Typhoid fever, Vibrio cholerae, and shigella species. Symptoms include fever and diarrhea, rashes, cramps, jaundice, liver disease, and other serious diseases, and while in many cases such ailments can be treated if attended to quickly, if not treated can worsen and cause permanent serious conditions as well as death, particularly in the young, elderly, and those having previously compromised immune systems.
In addition to untreated water, treated water supplies may also contain contaminants. While most cities and large towns in developed countries have large piped water systems that continually transport relatively high quality treated water to users, such tap water is only safe to drink if it has been fully treated and disinfected, and if the water system is well operated and maintained. Bottled-water is also increasingly popular, and although usually presumed to be safe by most users, may also be contaminated not only by microbial hazards such as those mentioned above but also by any number of chemical and physical hazards. Possible chemical hazards include lead, arsenic and benzene, while physical hazards include glass chips and metal fragments.
Numerous portable devices for filtering and purifying water in an attempt to render potable a water supply originating from untreated sources such as lakes and streams, or improperly maintained piped water supplies, and other sources are found in the prior art. For example, known are straw-type devices wherein the user places his or her mouth over one end of an elongated casing, and with the other end dangling in a water supply the user will suck inwardly in the same manner as with a conventional straw to cause water to pass into the device and move across one or more filters. A practical problem with such prior art suction filtering and purifying devices is that there is a practical limit to how small the pores in the filter elements, measured in microns and which pore size determines what size particles can pass through the filter, can be made. Although while of course the smaller the pore size of a filter, the more microbial and other contaminants will be removed from a solution upon being passed through the filter, with conventional straw filter devices the pore size of the filter cannot be made too small because it would become too difficult for users to draw water through the filter merely by exerting a manual sucking force. On the other hand, the pore sizes used with prior art manual straw type filter devices are too large to filter out many harmful contaminants, so that such prior art straws are not very effective. For example, while a maximum pore size of 4.0 microns will filter out Giardia cysts, a maximum pore size of 0.2 microns is required to filter out all bacteria, which generally have a size of between 0.2 and 10 microns. Many viruses, although typically ranging in size from 0.0004 to 0.1 microns which is too small to be filtered out by most filters, will attach themselves to a larger host bacteria and thus can be removed by removing the larger host bacteria. Another problem encountered with water filters in general is that the smaller the pore size of the filter, the more quickly it will become clogged and rendered ineffective, so that filters with smaller pore sizes must be cleaned or changed more often than filters having larger pore sizes. As a result, such filters must be replaced continually with a new, clean filter, since even if the filter is sterilized by dipping it in a bleach solution or the like to kill harmful parasites and the like, the contaminants although rendered no longer harmful if ingested nevertheless remain in the filter. Clogging filters is particularly problematic in less wealthy countries wherein even a portable filter device could be distributed to every member of the public, whereby everyone having a filtering device can obtain clean and potable water as long as the filter is new, but once the filter is clogged if a replacement filter is not available, or is too expensive, both of which situations are likely, the filter device will be rendered essentially useless.
Still another problem with known portable straw-type water filters is that the water cannot be isolated and treated with specific disinfecting agents for the contact time required by such agent to completely neutralize a contaminant. For example, a disinfectant such as iodine or chlorine must be mixed and in contact with the water for up to several minutes, which could not be accomplished with known portable water filtering devices. Others types of filtering and purifying devices are known, but they are bulky and inconvenient to carry and operate and thus are not truly portable. The present inventors have recognized the numerous problems associated with existing portable water filtering devices, and as a result of a significant amount of experimentation have now developed a portable water filtering and purifying device that can be carried easily in a backpack, bag, shoulder strap, or in a clothing pocket, and that removes almost all contaminants from an untreated water supply. With the present inventors' device, the water is first passed through a pre-filter which removes an unusually large number of contaminants before the water even enters the device. A pumping action is used to create a negative pressure in a first chamber, which pressure draws the contaminated water through the pre-filter, thus allowing the pre-filter to have a much smaller pore size and capture a greater number of contaminants than would otherwise be possible. Another unique feature is that a disinfecting agent such as chlorine may be placed in the pre-filter, which acts as a disinfecting chamber, so that the water is also disinfected once before entering the filter device. The water is then passed into a first chamber, where the water is again isolated and can be further subjected to any desired disinfecting or treatment agent for as long as needed. Then, the treated water supply is forced by a positive pressure out of the holding chamber into another chamber where it is further filtered and made potable. In a preferred embodiment, the water is mixed with a disinfecting agent in the pre-filter stage, a further treatment may be provided in the first chamber, and then the water is forced into the second chamber where it is passed over an activated carbon bed, and then through a nano-filter to provide complete purification. In the second chamber, a containment area in which micronutrients can be added to the water supply may be provided. In addition, the device can be used to clean and unclog the pre-filter by reverse flushing water through the pre-filter so that the device is quickly ready for re-use, thereby making the pre-filter reusable and extending its life more or less indefinitely. Other improvements include the provision of a combination filter cover and drinking cup, and treatment of the pre-filter with a nano silver coating to provide even greater protection against bacteria and viruses prior to entering the device. The present inventors' filter device thus have developed a portable water filter device that either removes or renders harmless virtually all contaminants present in a water supply.